Suppressing the oxidation of co to co2 in a fixed bed regenerator



Jan. 20, 1953 A. v. GROSSE 2,626,245

SUPPRESSING THE OXIDATION OF CO TO CO2 IN A FIXED BED REGENERATOR Original Filed July 22, 1949 Patented Jan. 20, 1953 UNITED STATES PATENT 'OFF ICE SUPPRESSINGTTHE OXIDATION F CD1-T0 C02 IN A FIXED rBED REGENERATOR Aristid V. Grosse, Haverford, Pa.

'10 '-Claims. l

'Ihis invention relates' to theremoval of carbon deposit vrfrom @petroleum cracking catalysts A'arid morefparticularly tothe-suppression of vcombustion inremoval of the AVcarbon deposit.

'I-n the processes for catalytic Vcracking nof petroleum used in the voil industry, it is essential to burnoff vthecarbon vdeposit accumulated on the crackingy catalyst. vThe 'heat `of this combustion is undesirable-'andv injurious to the-catalytic material. AAt ^the present time this Acombustion involvesA the transformation of the 'carbon into carbon 'dioxide w'ith release of its vattendant heat of combustion.

vIt is an -object o'f't'li'is invention to'reducethe heat of combustion accompanying'the' burning of 'carbon' depositifromVv petroleum crackingcatalysts.

It is another object of this invention, in removing ycarbon depositfrom catalytic material, to change it to carbon monoxide.

rIt isa'further object of 'this invention to suppress the `formation of carbon dioxide `in the burning of carbon deposit from cracking Vvcatalysts.

These and other objects. of this invention will become more apparent upon consideration of the following description, together with the drawing which is a diagrammatic showing of a plant for catalytic cracking.

'I'his application is adivision of the "co-pending application Serial Number 106,251 led July v22, 1949, now Patent No. 2,600,360.

Referring to the gure, three tanks I0, 20and 30 are shown in three cracking stages ina'iixe'd bed cracking apparatus. In each of these stages there is a bed of ycatalytic material made up of horizontal layers. Across and through this catalytic material the oil to :be 'cracked is 'fed fromoil lines I4. VDischarge lines Il, 2l vand 3l lead ffrom' the y"bottom "of each ofthe `'stages I0, mandan, respectively. Each of VtheseV lines II, 2| and 3l lconnects toareceiver I2, 22'1and32. Each of the' lines II, 2|*and 3| has a three-position valve 15. The Valves I5 control the ilow through the 'lines I I, 2 I' and 3l lsoqthat thetanks I0, 20`and vllcan be connectedto'receivers I2, 22 and 32, 'respectively,or the :lines II, 2| and. 3l can be connected to `discharge nozzles I6 for venting, -or the lines II. 2I and 3l can becompletely closed.

ATh'efo'lltozbe'cracked.sfed intorthe tanks l0., 20: and '30' through oil lines I4 which arevalve'd. to provide controlA overthe' feeding: of'lthe; cil.' iDescribing one method of operating .-ja .'iixedb'ed cracking apparatus as applied Lto thesysternv shown'inthe figure, o'il vis run` into tankv Igand cracked. "The products of the cracking are passed into. receiver I2. "The catalytic. material Which in oneform is porous pellets'becomes coked up by carbonideposit'from oil vapors. The increasing carbon deposit reduces the catalytic action until the accumulation'becomes so greateas to render the operation of the stage inefficient. It is necessary toremove the carbon from the catalyst .to `continue the operation of the cracking operation.

At the present time this carbon is removed-hy burningthe` carbon. off the catalyst. This is accomplished by closing theoil line into a stage and purging vthe catalyst Withsteam, or evacuating the chambenafter which a 'flow of 'dry airis passed `over the hot catalyst bed. The'eiect oi thexair is to oxidize the carbon 'deposit to'substantially carbon dioxide, which is drawn off through a suitable outlet.

The oxidation of carbon tocarbon dioxide'is accompanied by a large evolution of heat. It is the purpose of this invention to reduce the amount of heat thus evolved by limiting the oxidation ofthe carbon to carbon monoxide. The reaction of C-I-O2- CO2 has a `heat of'combu'stion of 94.385 cal/ mole as compared With the reaction of C+1O2 CO, Which has a heat of combustion of"26.428 cal/mole, at 18 C. To thus limit the oxidation of carbon a chemical suppressor is employed.

It has'been discovered that thechlorides and bromides of Asilicon vand toa lesser extent of aluminum, titanium and zirconium mixed togetherfwith free lchlorine or bromine are most effective; in suppressing the formation of carbon dioxide in the oxidation of carbon deposit from the catalytic material even in the presence of the :cracking catalyst. The employment of this suppressor'is Vvshown diagrammatica'lly in the figure. After a tank such as tank I0 hasbecome cokedup in the operation of this invention, the valve i9 from the oil line I4 is closed, the valve I5 .isset to connect yvent I6 to tank I0. The tank I0 is then evacuated. Oxidizing air is fed through asuppressor 'I'Ivwhere it passes througha liquid mixture of ya suppressorv solution, suchA as-silicon tetrachloride -and bromine. 'The suppressor saturatedl air is passed through line I3 and into tank lt'through valve 1'8. The `mixture oi-air'and suppressor is l heated toapproximately the Vcatalyst temperature where'the air oxldzesthe carbon deposit. ','This oxidation,- however, is limited largely to formation of carbon` monoxide Nwhich issldras'n 'off '.'throu'gh ivent y, IBawith any uncorn bined air. This process fits into the normal operation of the stages. As is customary in this type of operation, while tank I is being oxidized tank 20 in the next stage is being evacuated preparatory to oxidation while in tank 30 cracking is taking place. The steps are repeated stage by stage with cracking taking place in each tank after oxidation removes carbon from the catalyst.

By suppressing the production of carbon dioxide in favor of carbon monoxide the generation of heat in the oxidation of the carbon deposit is reduced. This is shown by the following example which serves to illustrate the process:

An alumina-silica cracking catalyst in smallY pellets in a pyrex glass reaction tube was coked by passing vapors of paran wax at about 500 C. over the catalyst pellets under usual cracking conditions. pressor mixture of silicon tetrachloride and bromine gas in the proportion of 5% by volume and oxygen gas was passed over the coked catalyst pellets at an initial catalyst temperature of 540 C.,and at a rate of 40 volumes of gas per volume of' catalyst per hour. The oxygen gas had an analysis of 94.6% O2, 0.0% CO2, and approximately 5% N2. The volumetric proportions of the suppressor mixture were two-thirds silicon tetrachloride and one-third liquid bromine. A

An oxidizing gas made up of a sup-l volumetric analysis of the exit gases from the oxidizing decarbonizing reaction showed 3.8% O2, 23% CO2, 69% CO and approximately 4% N2. Under the same conditions, but without a suppressor, the exit gas contained 0.6% Oz, 75% CO2, CO and about 5% N2.

The decarbonizing reaction generates 3600 calories per gram of carbon burned. By comparison, an identical oxygen gas without a suppressor mixture decarbonizing identical coked catalyst pellets under identical conditions generated 6700 calories per gram of carbon.

It is thus seen that when oxidizing the carbon deposit in the presence of a suppressor that large amounts of carbon monoxide are formed and comparatively small amounts of carbon dioxide, .and the oxidation releases substantially less heat than when a suppressor is absent.

The suppressor acts to combine with and render inactive hydrogen, be it in the free form or as Water, in and around the catalytic material. Itis a theory of this invention that this hydrogen is undesirable because of its catalytic effect on oxidation of carbon monoxide to carbon dioxide by oxygen. When carbon is burned in the presence of air carbon monoxide is first formed and it is a theory of this invention that as hydrogen acts as a catalyst in the oxidation of carbon monoxide by removing the hydrogen from the vicinity of the carbon oxidation reaction it is possible to limit this oxidation to the formation of monoxide.

One of the advantages of this invention as indicated above is reduction of heat in the removal of carbon deposit by oxidation. The problem of dissipating heat becomes much easier for the design engineer. New design possibilities heretofore considered impractical become available. A further advantage is the production of carbon monoxide in the place of carbon dioxide in the decarbonization of cracking catalysts. The carbon monoxide product can be converted to carbon dioxide in a subsequent operation in a suitable apparatus and the resultant heat recovered.

Thus while Ihave described my improvement in detail and with respect to certainpreferred forms, I do not desire to be limited to such details or forms since, as will be noticed by those skilled in the art, after understanding my invention many changes and modifications may be made and the invention embodied in widely different forms without departing from the spirit and scope thereof in its broader aspects, and I desire to cover all modifications, forms and improvements coming Within the scope of any one or more of the appended claims.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

l. In a process for decarbonizing a carbonized surface of a petroleum cracking catalyst, the steps comprising preparing an oxidation suppressor by mixing an elemental halogen selected from Vthe group consisting of chlorine and bromine with a bromide of an element selected from the group consisting ofsilicon, zirconium, titanium and aluminum; mixing said oxidation suppressor with an oxidizing gas, bringing said mixture of said oxidizing gas and oxidation suppressor into contact with said carbonized surface whereby said oxidation suppressor restricts the formation of carbon dioxide in the oxidation of the carbon of said carbonized surface and causes the formation of carbon oxides with carbon monoxide in the greater proportion.

2. In a process for decarbonizing a carbonized cracking catalyst surf-ace as claimed in claim 1, oxidizing said carbon to carbon oxides in the proportion of at least 60% carbon monoxide.

3. In a process for decarbonizing a carbonized g surface of a petroleum cracking catalyst, the

steps comprising preparing an oxidation suppressor by mixing elemental chlorine with a bromide of an element selected from the group consisting of silicon, zirconium, titanium and aluminum, mixing said oxidation suppressor with an oxidizing gas, bringing said -mixture of oxidizing gas and oxidation suppressor into contact with said carbonized surface, whereby said oxidation suppressor restricts the formation of carbon dioxide in the oxidation of the carbon of said carbonized surface and causes the formation of carbon oxides with carbon monoxide in the greater p-roportion.

4. In a process for decarbonizing a carbonized cracking catalyst surface as claimed in claim 1, the steps of placing said carbon oxidizing gas in contact with said contaminating carbon at a rate of about volumes of oxidizing gas per volume of catalyst per hour.

5. In a process for decarbonizing a carbonized surface of a petroleum cracking catalyst, the steps comprising preparing an oxidation suppressor by mixing elemental bromine with a bromide of an element selected from the group consisting of silicon, zirconium, titanium and aluminum, mixing said oxidation suppressor with an oxidizing gas, bringing said mixtureof oxidizing gas and oxidation suppressor into contact with said carbonized surface, whereby said oxidation suppressor restricts the formation of carbon dioxide in the oxidation of the carbon of said carcracking catalyst surface as claimed in claim 6, oxidizing said carbon to carbon oxides in the proportion of at least 60% carbon monoxide.

8. In the decarbonization of a carbonized cracking catalyst, the improvement which comprises oxidizing the carbonized cracking catalyst by contact of the carbonized catalyst with a mixture of an oxidizing gas and an oxidation suppressor composition made up of a bromide of an element selected from the group consisting of silicon, zirconium, titanium and aluminum together with a free halogen selected from the group consisting of bromine and chlorine whereby said oxidation suppressor composition restricts the formation of carbon dioxide in the oxidation of the carbon of said carbonized catalyst.

9. In the decarbonization of a carbonized cracking catalyst, the improvement which comprises oxidizing the carbonized cracking catalyst by contact of the carbonized catalyst with a mixture of an oxidizing gas and an oxidation suppressor composition made up of a bromide of an element selected from the group consisting of silicon, zirconium, titanium and aluminum together with a free chlorine whereby said oxidation suppressor composition restricts the formation of carbon dioxide in the oxidation oi the carbon of said carbonized catalyst.

10. In the decarbonization of a carbonized cracking catalyst, the improvement which comprises oxidizing the carbonized cracking catalyst by contact of the carbonized catalyst with a mixture of an oxidizing gas and an oxidation suppressor composition made up of a bromide of an element selected from the group consisting of silicon, zirconium, titanium and aluminum together with a free bromine whereby said oxidation suppressor composition restricts the formation of carbon dioxide in the oxidation of the carbon of said carbonized catalyst.

ARISTID V. GROSSE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,678,627 Jaeger July 24, 1928 2,396,157 Claussen Mar. 5, 1946 2,423,845 Myers July 15, 1947 

1. IN A PROCESS FOR DECARBONIZING A CARBONIZED SURFACE OF A PETROLEUM CRACKING CATALYST, THE STEPS COMPRISING PREPARING AN OXIDATION SUPPRESSOR BY MIXING AN ELEMENTAL HALOGEN SELECTED FROM THE GROUP CONSISTING OF CHLORINE AND BROMINE WITH A BROMIDE OF AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF SILICON, ZIRCONIUM, TITANIUM AND ALUMINUM, MIXING SAID OXIDATION SUPPRESSOR WITH AN OXIDIZING GAS, BRINGING SAID MIXTURE OF SAID OXIDIZING GAS AND OXIDATION SUPPRESSOR INTO CONTACT WITH SAID CARBONIZED SURFACES WHEREBY SAID OXIDATION SUPPRESSOR RESTRICTS THE FORMATION OF CARBON DIOXIDE IN THE OXIDATION OF THE CARBON OF SAID CARBONIZED SURFACE AND CAUSES THE FORMATION OF CARBON OXIDES WITH CARBON MONOXIDE IN THE GREATER PROPORTION. 